DESCRIPTION: The genus Leptospira contains a number of important human pathogens, but little is known about this group of spirochetes, especially at the genetic level. Dr. Ralph has discovered that the 23S ribosomal RNA (rRNA) genes of many strains of Leptospira spp. contain intervening sequences (IVS), which are removed after RNA synthesis so that the actual form of the 23S rRNA in the ribosome is a cut form. Based on the structure of the processed form of the rRNA, the investigator suggests that the two pieces of the processed rRNA are held together by a short region of base pairing and this allows a functional ribosome to be formed even though the rRNA has been nicked. The IVS contain an open reading frame, which could encode a proteins. Finally, the investigator has evidence based on phylogenetic analysis suggesting that the IVS have been transferred horizontally. A major goal of the proposal is to investigate further the processing step that removes the IVS from the rRNA and to determine the function of the open reading frame (orf) encoded in the IVS. A second major goal is to demonstrate horizontal transfer of the IVS between strains of Leptospira. He also proposes to continue to examine the genetic variability within the genus, using a restriction site polymorphism approach he developed, and to obtain and characterize further examples of IVS from new isolates, but these goals account for only a minor part of the proposed work.